The Influence of Geometry on the Vibronic Spectra of Quantum Aggregates

TL;DR

This paper investigates how the geometry and orientation of molecules in aggregates influence their vibronic spectra, demonstrating that small geometric changes can significantly alter spectral features, using a generalized CES approximation.

Contribution

It introduces a generalized coherent exciton scattering (CES) method applicable to aggregates of any size and shape, highlighting the impact of geometry on vibronic spectra.

Findings

Small geometric changes drastically affect vibronic spectra.

The generalized CES method is effective for arbitrary aggregate geometries.

Excitonic state localization depends on geometry, not disorder.

Abstract

A study is presented of the localisation of excitonic states on extended molecular aggregates composed of identical monomers arising, not from disorder due to statistical energy shifts of the monomers, induced by environmental interactions (Anderson localisation), but rather simply due to changes in the orientation and geometrical arrangement of the transition dipoles. It is shown further that such small changes nevertheless can have a drastic effect on the shape of the vibronic spectrum of the aggregate. The vibronic spectra are calculated using the "coherent exciton scattering" (CES) approximation whose derivation we generalise to be applicable to aggregates of arbitrary size and geometry.